The Bell Catalyst 200 Mini U-lock, featuring a 6" hardened steel shackle and crossbar, is small enough to fit in your backpack, tote, or back pocket. The short shackle also provides less space for leveraging tools used to break locks. The Catalyst 200 comes with two standard keys that can be registered after purchase online, see packaging instructions on how to register. In the event registered keys are lost, Bell will send replacements at no charge. An independent lab has rated the security of this lock a 3 on a 5 point scale. Perfect for locking your bike in low to medium crime areas.